The present invention generally relates to a method for preparing sol-gel particles that encase or encapsulate or entrap (hereinafter called loading) functional molecules or substances. The term "functional molecules or substances" in the present invention relates to any molecules or substances that can be used in agriculture and industry.
Isolating functional molecules or substances in inert matrices has many useful benefits and applications where chemical contact between the functional molecules and the immediate environment should be minimized. For example, make-up compositions, such as make-up colors are currently using a very limited number of approved natural pigments and even fewer artificial organic colors. Many dyes and pigments with desired color shades of natural or synthetic origin are not approved for skin contact because their safety for direct skin contact has not been demonstrated. Isolating the colorants in transparent and inert isolating material provides a way to prevent the direct contact between the color molecules and the skin, while retaining (or even enhancing) the color intensity. Another very important application is in sunscreen compositions. The active ingredients in sunscreens have been reported to cause contact dermatitis and may cause photocontact dermatitis. Moreover, the light-excited species of these reagents may undergo photodecomposition reactions resulting in the production of free radicals and reactive oxygen species, which may bear deleterious effects on live tissues. Thus, encapsulating sunscreen active ingredients in a transparent matrix like silica offers a sophisticated way to benefit from the light-absorbing capability of sunscreens, while substantially isolating them and/or their possible photodecomposition products from the live tissues. Another example, from a totally different field, is the encapsulating of food colors either for prolonging the shelf life of food products containing unstable natural colors such as lycopene and carotene or for isolating artificial food colors that have undesirable side effects. Encapsulating food colors of the second type in inert transparent microcapsules provides a way to prevent the digestion of these colorants while maintaining their desired color effect.
Recognizing that metal and semi metal alkoxide monomers (and their partially hydrolyzed and condensed polymers) such as tetramethoxy silane (TMOS), tetraethoxy silane (TEOS), methyl triethoxy silane (MeTEOS) etc. are very good solvents for numerous molecules and substances facilitated the development of this method, which utilizes this solubility to load the dissolved molecules or substances in the hydrolysis-condensation polymer of the monomer solvent. Nonetheless, the present invention may also be used to coat or load particles or substances which can be suspended in the sol-gel precursors.
The current invention reveals how to obtain sol-gel materials containing high loading of active ingredients, up to 95% (w/w). Such high loading is required, for example, in order to obtain high Sun Protection Factor (SPF) values. It also facilitates the entrapment or encapsulation of many other molecules or substances, where the application may demand high loading of the entrapped molecule or substance.
The loaded molecules or substances can be any molecules or substances that are soluble or that can be suspended in the metal or semi-metal alkoxides of choice. Examples for such molecules or substances are: ultra-violet absorbing molecules or reflecting substances used in sunscreens, fragrances, perfume, colors and dyes, food colors and food additives, antioxidants, humidifiers, vitamins, explosives, insecticides, herbicides and fungicides, or biological molecules such as enzymes or antibodies, as well as various drugs, catalysts and reagents.
The current invention further teaches how to obtain controlled physical form of the product. In a preferred embodiment, it teaches how to obtain capsules and microcapsules of sol-gel derived material, containing the loaded molecule or substance, with a smooth and pleasant contact.
The product by process may accordingly vary for human or non-human applications, as the obtained aqueous suspension and the obtained dry powder may be easily incorporated in various carriers, such as creams and lotions, processed food, sprays, paints, lacquers, coatings, plastics and detergents.